Look at the crash at
http://www.youtube.com/watch?v=TMl-WQ5XkMI . Time from hitting wall at 45mph to dead stop of around 70 milliseconds, so 0.07 seconds. Acceleration = -287m/s/s.
Force = mass x acceleration so you get an effective weight of a 650L tank during that deceleration of 186 tons. A 1000L tank would be about 287 tons.
Now the news is that that was an empty van in the video, so your full van will take more time to stop and increase the amount of the van that crumples, but the numbers are a good indication of the scale of the problem. If your luggage hooks/straps can't take a couple of hundred tons then you're going to have a headache.
Before you all respond, I
know I'm wrong and that your mate was unharmed a 200mph crash with a 2 ton bale of paper in the back secured with a bungee cord to a paper clip round the back bumper but the physics is unassailable. I also know that you've never heard of anyone being hurt in an accident so it can't possibly happen.
Vin